1. Field of the Invention
This invention relates generally to an exchangeable catheter, and more particularly to a catheter which is convertible from one which permits simple and rapid exchange of catheters while a guidewire is in place to a catheter which allows guidewires to be exchanged while the catheter is in place.
2. Brief Description of the Prior Art
Various configurations of catheters and guidewires have been developed over the years for the purpose of satisfying different functional requirements. "Over-the-wire" catheter systems permit full rotational and full coaxial mobility of the guidewire relative to the catheter component of the system. "Over-the-wire" catheters can be fully withdrawn over a guidewire, and they will accept the antegrade and retrograde introduction of a guidewire therethrough. U.S. Pat. No. 4,323,071 describes an "over-the-wire" system.
While "over-the-wire" systems allow for exchange of catheters along the fixed guidewire and vice versa, such replacement is mechanically difficult because "over-the-wire" systems require that the guidewire protrude from the patient's body by a length greater than the length of the catheter. Thus, manipulation of the catheter during catheter replacement is difficult.
A different type of catheter-guidewire system has been developed to address this problem. Known generically as "rapid exchange" or "monorail" catheters, the design permits catheter exchange over a standard 175 cm length guidewire. U.S. Pat. Nos. 4,762,129 to Bonzel, 4,748,982 to Horzewski et al., and 5,040,548 to Yock teach variations of such designs. The designs include an inflation lumen within the catheter which runs the length of the catheter, and a separate guidewire lumen which extends a relatively short distance from the distal end toward the proximal end of the catheter. Since the guidewire lumen is relatively short compared to the overall length of the catheter, when one catheter is withdrawn over the guidewire and replaced with another guidewire, only the relatively short guidewire lumen needs to be threaded over the fixed guidewire.
The "monorail" concept has been readily accepted because it permits simple and rapid catheter exchange. However, a major problem of the design is that once a "monorail" catheter has been positioned, the guidewire is extremely difficult to exchange. This is because the guidewire lumen is relatively short. When the catheter is in place and the guidewire is withdrawn, it is impractical to locate the guidewire lumen with a replacement guidewire while the "monorail" catheter (and entrance to the guidewire lumen) is within a patient's body.